But the representative from New York says he hasn’t given up: In the next few months, Israel's office tells WIRED he plans to reintroduce legislation that would ban 3-D printed guns or any other fully-plastic firearm. The Undetectable Firearms Modernization Act, which Israel first tried and failed to pass last year, forbids the possession or manufacture of any gun that could slip through a standard metal detector unnoticed, including those that include a removable chunk of non-functional metal—what he sees as a loophole in the current law against plastic weapons.

“My legislation is about making sure that we have laws in place to ensure that criminals and terrorists can’t produce guns that can easily be made undetectable. Security checkpoints will do little good if criminals can produce plastic firearms and bring those firearms through metal detectors into secure areas like airports or courthouses,” Israel wrote in a statement to WIRED. “When I started talking about the issue of completely plastic firearms, I was told the idea of a plastic gun is science-fiction. That science-fiction is now a dangerous reality.”

Since Israel first began focusing on 3-D printed weapons as an issue, he has shifted from seeking to specifically forbid their printing to instead banning all undetectable weapons—an umbrella he intends to include 3-D printed ones. “What we’re trying to do is make it clear that if you choose to construct a weapon or weapon component using a 3-D printer, and it’s homemade, you’ll be subject to penalties,” Israel told me in early 2013. More recently he’s made clear that he doesn’t intend to target 3-D printing specifically: The bill he introduced at the end of 2013 never mentioned 3-D printing by name.

But Israel’s bill does seem designed to address weapons like the Liberator, a one-shot 3-D printed pistol whose digital blueprints were released by the gun access group Defense Distributed in 2013. The Liberator, as manufactured and demonstrated by Defense Distributed’s founder Cody Wilson, was technically detectable by a standard metal detector, because it included a chunk of steel in its body to comply with the current Undetectable Firearms Act. But that piece was entirely non-functional and could be removed at any time.

Like the bill he already introduced, the new one will require that crucial functional components be made of detectable metal. In rifles and shotguns, the combination of the slide, barrel and receiver would have to be as detectable as a 3.7-ounce piece of steel. In handguns, the same would be required of the gun’s cylinder and barrel. All of that would make a working, fully 3-D printed gun essentially impossible to legally produce.

The currently active Undetectable Firearms Act, by contrast, merely demands that the entire gun be as detectable as that 3.7 ounce chunk of steel. And while that law was renewed last year, Israel failed to push through his changes to it. That's perhaps no surprise given congress's general unwillingness to pass any gun control law. The renewal of the Undetectable Firearms Act was the only gun control law passed last year. "Current law is completely inadequate, and though for my Republican colleagues it was easier to live with current law than to expand it, it is critical that we continue the national dialogue about undetectable fire arms," Israel writes to WIRED.

The new bill would make a working, fully 3-D printed gun essentially impossible to legally produce.

What the congressman hasn't addressed is how the bill might have better luck this time around. Congress, after all, has only become more Republican since the 2014 mid-term elections. When his Undetectable Firearms Modernization Act was introduced last time around, the legislation was co-sponsored by Republican Representative Peter King. Israel's office wouldn't comment on whether any Republican might co-sponsor the bill this time, and King's office didn't respond to a request for comment.

But Israel may be thinking that the technological advancement of 3-D printed guns will push them back into the national conversation. Since he first began raising the issue, after all, home-printed firearms have taken leaps forward in accessibility, durability, and power. And Defense Distributed's latest project seeks to develop a gun that can be 3-D printed in carbon fiber, a material that has a higher strength-to-weight ratio than aluminum. The result could be homemade, undetectable weapons that are far more practical than the original Liberator. A single real-world incident involving those potentially deadly weapons would bring them back into the spotlight.

But even Israel's bill, it's important to note, doesn't deal with all the recent advancements in DIY gunsmithing. It wouldn't prevent anyone from 3-D printing a lower receiver for their AR-15, for instance—the most regulated component of the semi-automatic weapon. Anyone could still print just that one piece and buy the rest of the weapon online legally. Defense Distributed's latest project has been selling computer-controlled mills that carve those lower receivers out of aluminum, another way to obtain a semi-automatic weapon with no serial number that still wouldn't violate Israel's bill's undetectability requirements.

Supporters of 3-D printing were initially wary of Israel's bill, which in his initial statements appeared to be the first attempt to regulate the emerging technology. But the Congressman's general focus on gun detectability rather than any particular manufacturing process is a better approach, says Michael Weinberg, a 3-D printing-focused analyst with the non-profit Public Knowledge who recently took a job as general counsel of the 3-D printing firm Shapeways. "What we didn’t want to happen was a situation where 3-D printing of guns explicitly was made illegal," says Weinberg. "There are a lot of ways to make undetectable firearms, and if you focus on each one you’ll end up with pretty ineffective legislation."

The NRA, not surprisingly, isn't so supportive. "The NRA strongly opposes ANY expansion of the Undetectable Firearms Act, including applying the UFA to magazines, gun parts, or the development of new technologies," reads a statement from the group's website. "We will continue to aggressively fight any expansion of the UFA or any other proposal that would infringe on our Second Amendment rights."

On the other side of the gun debate, however, gun control advocates' support for the bill isn't quite so unequivocal. The gun control group the Brady Campaign, for its part, says it agrees that homemade and 3-D printed guns represent a real issue. "As technology continues to advance and it becomes possible to make guns in homes and garages across the country, it creates a dangerous loophole for domestic abusers, felons and other criminals to make guns without any background checks and use them to harm others," a spokesperson writes to WIRED. "Any gun made should not be able to slip through security checkpoints and certainly should not slip into the hands of dangerous people."

But not every gun control group sees homemade or undetectable weapons as such a high priority. "The notion that a mass shooter or a street criminal is going to buy a 3-D printer, download blueprints, and try a few test runs before producing their own gun is very unlikely," says Ladd Everitt, the communications director for the Coalition to Stop Gun Violence. "It’s a hassle, when you can just buy a gun with zero accountability in this country."

Everitt says he sees the issue of undetectable 3-D printed guns as having less to do with run-of-the-mill gun violence than with the possibility of a terrorism threat, given the weapons' potential to bypass both background checks and security checkpoints. "I would salute any legislator on Capitol Hill being forward-looking at thinking about how we can deal with this problem," he says. "But in the overall universe of gun laws, this is not at the top of our list."

Those sorts of comments from even gun control advocates suggest an uncertain outcome for Israel's bill. The technological future of 3-D printed guns, meanwhile, looks brighter every day.